Myujth

I have a Firestore collection tree in which I plan to store only one document. I want to check if that collection contains that document and if so, retrieve the id of the document! Any ideas/thoughts?

Thanks :)

Try this one.

FirebaseFirestore firestore = FirebaseFirestore.getInstance();
firestore.collection("users").whereEqualTo("user_uid", user.getUid())
 .limit(1).get()
 .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() 
 @Override
 public void onComplete(@NonNull Task<QuerySnapshot> task) 
 if (task.isSuccessful()) 
 boolean isEmpty = task.getResult().isEmpty();
 
 
 );

Make the document structure like this one:

collectionName(Collection) -> documentId(Document) -> id = documentId(and other fields)

Now make a query:

FirebaseFirestore firestoreDatabase= FirebaseFirestore.getInstance();
firestoreDatabase.collection(COLLECTION_NAME)
 .whereEqualTo(DOCUMENT_ID, documentId)
 .get()
 .addOnCompleteListener(task -> 
 if (task.isSuccessful()) 
 if (task.getResult().getDocuments().size() > 0)
 // Here is your document with id
 
 );

If you want to check a particular document for existence based on its document id, please use the following lines of code:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
DocumentReference docIdRef = rootRef.collection("yourCollection").document(docId);
docIdRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() 
 @Override
 public void onComplete(@NonNull Task<DocumentSnapshot> task) 
 if (task.isSuccessful()) 
 DocumentSnapshot document = task.getResult();
 if (document.exists()) 
 Log.d(TAG, "Document exists!");
 else 
 Log.d(TAG, "Document does not exist!");
 
 else 
 Log.d(TAG, "Failed with: ", task.getException());
 
 
);

If you don't have the document id, you need to use a query and find that document according to a value of a specific property like this:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference yourCollRef = rootRef.collection("yourCollection");
Query query = yourCollRef.whereEqualTo("yourPropery", "yourValue");
query.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() 
 @Override
 public void onComplete(@NonNull Task<QuerySnapshot> task) 
 if (task.isSuccessful()) 
 for (QueryDocumentSnapshot document : task.getResult()) 
 Log.d(TAG, document.getId() + " => " + document.getData());
 
 else 
 Log.d(TAG, "Error getting documents: ", task.getException());
 
 
);